Chip resistor, method of producing chip resisitor and chip resistor packaging structure

ABSTRACT

[Object] 
     A method for efficiently manufacturing chip resistors is provided. 
     [Means] 
     The method includes the steps of preparing at least three conductive elongated boards  711  made of an electrically conductive material and a resistive member  702  made of a resistive material, arranging the at least three conductive elongated boards  711  apart from each other along a width direction crossing a longitudinal direction in which one of the at least three conductive elongated boards  711  is elongated, forming a resistor aggregate  703  by bonding the resistive member  702  to the at least three conductive elongated boards  711 , and collectively dividing the resistor aggregate  703  into a plurality of chip resistors by punching so that each of the chip resistors includes two electrodes and a resistor portion bonded to the two electrodes.

TECHNICAL FIELD

The present invention relates to a chip resistor, a method formanufacturing a chip resistor, and a mount structure of a chip resistor.

BACKGROUND ART

A conventionally known chip resistor (surface mount resistor) includestwo leads and a central resistor portion. The central resistor portionis sandwiched between the two leads and bonded to the leads. This typeof chip resistor is manufactured by using a plurality of reels.Specifically, a strip of a resistive material is wound around one of thereels, whereas a strip of an electrically conductive material is woundaround each of other two reels. The strips are paid out from the reelswhile rotating the reels, and bonded together in such a manner that thestrip of the resistive material is sandwiched between the two strips ofan electrically conductive material. The strips bonded together are cutsuccessively.

TECHNICAL REFERENCE Patent Document

-   Patent Document 1: Japanese Patent No. 3321724

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

The present invention has been conceived under the above-describedcircumstances. It is therefore an object of the present invention toprovide a method for efficiently manufacturing a chip resistor.

Means for Solving the Problems

According to a first aspect of the present invention, there is provideda chip resistor manufacturing method comprising the steps of: preparingat least three conductive elongated boards made of an electricallyconductive material and a resistive member made of a resistive material;arranging the at least three conductive elongated boards apart from eachother along a width direction crossing a longitudinal direction in whichone of the at least three conductive elongated boards is elongated;forming a resistor aggregate by bonding the resistive member to the atleast three conductive elongated boards; and collectively dividing theresistor aggregate into a plurality of chip resistors by punching sothat each of the chip resistors includes two electrodes and a resistorportion bonded to the two electrodes.

Preferably, the step of forming a resistor aggregate uses welding.

Preferably, the step of forming a resistor aggregate uses high energybeam welding.

Preferably, the step of forming a resistor aggregate uses electron beamwelding or laser beam welding as the high energy beam welding.

Preferably, the method further comprises the step of bending one of theat least three conductive elongated boards.

Preferably, the bending step is performed at the same time as thecollectively dividing step.

Preferably, one of the at least three conductive elongated boards has athickness smaller than the thickness of the resistive member.

Preferably, the resistive member includes a plurality of resistiveelongated boards, and the step of forming a resistor aggregate comprisesbonding each of the resistive elongated boards to two of the at leastthree conductive elongated boards.

Preferably, the step of forming a resistor aggregate comprises arrangingeach of the resistive elongated boards between adjacent two of the atleast three conductive elongated boards.

Preferably, the step of forming a resistor aggregate comprises arrangingeach of the resistive elongated boards at a position overlappingadjacent two of the at least three conductive elongated boards as viewedin the thickness direction perpendicular to both of the longitudinaldirection and the width direction.

According to a second aspect of the present invention, there is provideda chip resistor comprising: a first electrode; a second electrode spacedapart from the first electrode in a first direction; and a resistorportion bonded to the first electrode and the second electrode. Theresistor portion extends along a plane spreading in the first directionand a second direction crossing the first direction. The first electrodeincludes a first side surface facing in the first direction, a secondside surface facing in the second direction, and a curved surfaceconnected to both the first side surface and the second side surface.

Preferably, the chip resistor further comprises a first intermediatelayer connected to the first electrode and the resistor portion, and asecond intermediate layer connected to the second electrode and theresistor portion. The first intermediate layer and the secondintermediate layer are made of a same material.

Preferably, the resistor portion is sandwiched between the firstelectrode and the second electrode.

Preferably, the first intermediate layer includes a wide portion and anarrow portion. The wide portion is exposed to a third directioncrossing both of the first direction and the second direction. Thedimension of the narrow portion in the first direction is smaller thanthe dimension of the wide portion in the first direction.

Preferably, the first electrode and the second electrode are on a sameside of the resistor portion.

Preferably, the first side surface includes a linear trace formedsurface formed with a linear trace, and a breakage trace formed surfaceconnected to the linear trace formed surface and formed with a breakagetrace.

Preferably, the first electrode includes a plate-like portion extendingalong the first direction and the second direction and an inclinedportion inclined with respect to the plate-like portion and closer tothe resistor portion than the plate-like portion is.

Preferably, the resistor portion has a thickness smaller than thethickness of the first electrode.

According to a third aspect of the present invention, there is provideda chip resistor manufacturing method comprising the steps of: preparingtwo conductive elongated boards made of an electrically conductivematerial and a resistive elongated board made of a resistive material;arranging the resistive elongated board between the two conductiveelongated boards; bonding each of the two conductive elongated boards tothe resistive elongated board; and cutting, by shearing, the twoconductive elongated boards and the resistive elongated board along awidth direction crossing a longitudinal direction in which one of thetwo conductive elongated boards is elongated.

Preferably, the method further comprises the step of bending each of theconductive elongated boards.

Preferably, the bending step is performed at the same time as thecutting step.

Preferably, the bonding step uses welding.

Preferably, the bonding step uses high energy beam welding.

Preferably, the bonding step uses electron beam welding or laser beamwelding as the high energy beam welding.

Preferably, the method further comprises the step of fixing each of thetwo conductive elongated boards to the resistive elongated board beforethe bonding step. The bonding step comprises performing welding, witheach of the two conductive elongated boards fixed to the resistiveelongated board.

Preferably, the fixing step comprises sandwiching the two conductiveelongated boards and the resistive elongated board by a first clampingtool and a second clamping tool. The sandwiching step comprises pressingone of the two conductive elongated boards against the resistiveelongated board by the first clamping tool and pressing the other one ofthe two conductive elongated boards against the resistive elongatedboard by the second clamping tool.

Preferably, the arranging step comprises placing the two conductiveelongated boards and the resistive elongated board on a base. The fixingstep comprises pressing the two conductive elongated boards and theresistive elongated board placed on the base against the base by apressing tool. The pressing tool is formed with two elongated holesextending in one direction. The step of pressing against the basecomprises arranging one of the two elongated holes to overlap a portionwhere one of the two conductive elongated boards and the resistiveelongated board are in contact with each other and arranging the otherone of the two elongated holes to overlap a portion where the other oneof the two conductive elongated boards and the resistive elongated boardare in contact with each other. The bonding step comprises directinghigh energy beam so as to pass through each of elongated holes.

According to a fourth aspect of the present invention, there is provideda chip resistor comprising: a first electrode; a second electrode spacedapart from the first electrode in a first direction; and a resistorportion bonded to the first electrode and the second electrode. Thefirst electrode includes a front surface and a reverse surface whichface away from each other. The resistor portion extends along a planespreading in the first direction and a second direction crossing thefirst direction. The first electrode includes a first electrode sidesurface facing to a first side in the second direction and a secondelectrode side surface facing to a second side in the second direction.The first electrode side surface includes a first electrode linear traceformed surface formed with a linear trace, and a first electrodebreakage trace formed surface connected to the first electrode lineartrace formed surface and formed with a breakage trace. The firstelectrode linear trace formed surface is closer to the front surfacethan the first electrode breakage trace formed surface is.

Preferably, the second electrode side surface includes a secondelectrode linear trace formed surface formed with a linear trace, and asecond electrode breakage trace formed surface connected to the secondelectrode linear trace formed surface and formed with a breakage trace.The second electrode linear trace formed surface is closer to thereverse surface than the second electrode breakage trace formed surfaceis.

Preferably, the resistor portion includes a resistor portion frontsurface and a resistor portion reverse surface which face away from eachother, a first resistor portion side surface facing to a first side inthe second direction, and a second resistor portion side surface facingto a second side in the second direction. The resistor portion frontsurface faces to the same direction as the front surface. The firstresistor portion linear trace formed surface is closer to the resistorportion front surface than the first resistor portion breakage traceformed surface is.

Preferably, the second resistor portion side surface includes a secondresistor portion linear trace formed surface formed with a linear trace,and a second resistor portion breakage trace formed surface connected tothe second resistor portion linear trace formed surface and formed witha breakage trace. The second resistor portion linear trace formedsurface is closer to the resistor portion reverse surface than thesecond resistor portion breakage trace formed surface is.

Preferably, the first resistor portion breakage trace formed surface hasa width larger than the width of the first electrode breakage traceformed surface.

Preferably, the first electrode linear trace formed surface has a widththat increases as proceeding further away from the resistor portion.

Preferably, the chip resistor further comprises a first intermediatelayer connected to the first electrode and the resistor portion, and asecond intermediate layer connected to the second electrode and theresistor portion. The first intermediate layer and the secondintermediate layer are made of a same material.

Preferably, the resistor portion is sandwiched between the firstelectrode and the second electrode.

Preferably, the first intermediate layer includes a wide portion and anarrow portion. The wide portion is exposed to a third directioncrossing both of the first direction and the second direction. Thedimension of the narrow portion in the first direction is smaller thanthe dimension of the wide portion in the first direction.

Preferably, the first electrode includes a plate-like portion extendingalong the first direction and the second direction and an inclinedportion inclined with respect to the plate-like portion and closer tothe resistor portion than the plate-like portion is.

According to a fifth aspect of the present invention, there is provideda chip resistor mount structure comprising a chip resistor providedaccording to the second or the fourth aspect of the present invention, amount board, and a solder layer between the mount board and the chipresistor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a mount structure of a chip resistoraccording to a first embodiment of the present invention;

FIG. 2 is a sectional view taken along lines II-II in FIG. 1;

FIG. 3 is a sectional view taken along lines V-V in FIG. 1;

FIG. 4 is a plan view of amount structure of the chip resistor shown inFIG. 1;

FIG. 5 is a view (partially omitted) along lines V-V in FIG. 1;

FIG. 6 is a front view of the chip resistor shown in FIG. 1;

FIG. 7 is a partially enlarged sectional view taken along lines VII-VIIin FIG. 6;

FIG. 8 is a plan view showing a step of a method for manufacturing thechip resistor according to the first embodiment of the presentinvention;

FIG. 9 is a partial sectional view taken along lines IX-IX in FIG. 8;

FIG. 10 is a plan view showing a step of a method for manufacturing thechip resistor according to the first embodiment of the presentinvention;

FIG. 11 is a partial sectional view taken along lines XI-XI in FIG. 10;

FIG. 12 is a plan view showing a step of a method for manufacturing thechip resistor according to the first embodiment of the presentinvention;

FIG. 13 is a partial sectional view taken along lines XIII-XIII in FIG.12;

FIG. 14 is a plan view showing the step subsequent to the step of FIG.12;

FIG. 15 is a partial sectional view taken along lines XV-XV in FIG. 14;

FIG. 16 is a partial sectional view showing the step subsequent to thestep of FIG. 15;

FIG. 17 is a plan view of a step of a variation of a method formanufacturing the chip resistor according to the first embodiment of thepresent invention;

FIG. 18 is a sectional view taken along lines XVIII-XVIII in FIG. 17;

FIG. 19 is a sectional view of a mount structure of a chip resistoraccording to a second embodiment of the present invention;

FIG. 20 is a sectional view taken along lines XX-XX in FIG. 19;

FIG. 21 is a sectional view taken along lines XXI-XXI in FIG. 19;

FIG. 22 is a plan view of the chip resistor mount structure shown inFIG. 19;

FIG. 23 is a view (partially omitted) along lines XXIII-XXIII in FIG.19;

FIG. 24 is a sectional view of a mount structure of a chip resistoraccording to a third embodiment of the present invention;

FIG. 25 is a plan view of the chip resistor mount structure shown inFIG. 24;

FIG. 26 is a view (partially omitted) along lines XXVI-XXVI in FIG. 24;

FIG. 27 is a plan view showing a step of a method for manufacturing thechip resistor according to the third embodiment of the presentinvention;

FIG. 28 is a partial sectional view taken along lines XXVIII-XXVIII inFIG. 27;

FIG. 29 is a sectional view of a mount structure of a chip resistoraccording to a fourth embodiment of the present invention;

FIG. 30 is a sectional view taken along lines XXX-XXX in FIG. 29;

FIG. 31 is a sectional view taken along lines XXXI-XXXI in FIG. 29;

FIG. 32 is a plan view of the chip resistor mount structure shown inFIG. 29;

FIG. 33 is a view (partially omitted) along lines XXXIII-XXXIII in FIG.29;

FIG. 34 is a front view of the chip resistor shown in FIG. 29;

FIG. 35 is a rear view of the chip resistor shown in FIG. 29;

FIG. 36 is a perspective view showing a step of a method formanufacturing the chip resistor according to the fourth embodiment ofthe present invention;

FIG. 37 is a plan view of FIG. 36;

FIG. 38 is a sectional view taken along lines XXXVIII-XXXVIII in FIG.37;

FIG. 39 is a perspective view showing the step subsequent to the step ofFIG. 36;

FIG. 40 is a plan view showing the step subsequent to the step of FIG.39;

FIG. 41 is a sectional view taken along lines XLI-XLI in FIG. 40;

FIG. 42 is a sectional view showing the step subsequent to the step ofFIGS. 40 and 41;

FIG. 43 is a sectional view showing the step subsequent to the step ofFIG. 42;

FIG. 44 is a sectional view taken along lines XLIV-XLIV in FIG. 43;

FIG. 45 is a sectional view showing the step subsequent to the step ofFIG. 44;

FIG. 46 is a sectional view of a mount structure of a chip resistoraccording to a fifth embodiment of the present invention;

FIG. 47 is a perspective view showing a step of a method formanufacturing the chip resistor according to the fifth embodiment of thepresent invention;

FIG. 48 is a plan view showing the step subsequent to the step of FIG.47; and

FIG. 49 is a sectional view taken along lines XLIX-XLIX in FIG. 48.

MODE FOR CARRYING OUT THE INVENTION

A first embodiment of the present invention is described below withreference to FIGS. 1-18.

FIG. 1 is a sectional view of a mount structure of a chip resistoraccording to this embodiment. FIG. 2 is a sectional view taken alonglines II-II in FIG. 1. FIG. 3 is a sectional view taken along linesIII-III in FIG. 1. FIG. 4 is a plan view of a mount structure of thechip resistor shown in FIG. 1. FIG. 5 is a view (partially omitted)along lines V-V in FIG. 1.

The chip resistor mount structure 800 shown in these figures includes achip resistor 101, a mount board 801 and a solder layer 802.

For instance, the mount board 801 is a printed circuit board. Forinstance, the mount board 801 includes an insulating substrate and apattern electrode (not shown) formed on the insulating substrate. Thechip resistor 101 is mounted on the mount board 801. The solder layer802 is between the chip resistor 101 and the mount board 801. The solderlayer 802 bonds the chip resistor 101 and the mount board 801 to eachother.

FIG. 6 is a front view of the chip resistor shown in FIG. 1.

The chip resistor 101 includes a first electrode 1, a second electrode2, a resistor portion 3, a first intermediate layer 4 and a secondintermediate layer 5.

The first electrode 1 is made of an electrically conductive material.Examples of the electrically conductive material include Cu, Ni and Fe.When the chip resistor 101 is mounted on the mount board 801, the firstelectrode 1 is bonded to the solder layer 802. The first electrode 1 iselectrically connected to the pattern electrode (not shown) of the mountboard 801 via the solder layer 802. In this embodiment, the firstelectrode 1 includes a plate-like portion 181 and an inclined portion182.

The plate-like portion 181 extends along the X-Y plane. The plate-likeportion 181 constitutes the most part of the first electrode 1. Theinclined portion 182 is inclined with respect to the X-Y plane.Specifically, the inclined portion 182 is inclined to be deviated towardthe direction Z1 as proceeding further away from the plate-like portion181. The inclined portion 182 is in the form of a strip extending alongthe direction Y. The inclined portion 182 is connected to the plate-likeportion 181.

The first electrode 1 includes a front surface 11, a reverse surface 12,two side surfaces 13 (first side surfaces), a side surface 14 (secondside surface), and two curved surfaces 15.

The front surface 11 faces to the direction Z1, whereas the reversesurface 12 faces to the direction Z2. Each of the side surfaces 13, 14and the curved surfaces 15 face to a direction perpendicular to thedirection Z. Specifically, the side surfaces 13 face to the direction Yand the side surface 14 faces to the direction X. The curved surfaces 15are connected to the side surfaces 13 and the side surface 14.

FIG. 7 is a partially enlarged sectional view taken along lines VII-VIIin FIG. 6.

The side surface 13 includes a linear trace formed surface 131 and abreakage trace formed surface 132. The linear trace formed surface 131is formed with a linear trace. The linear trace comprises a plurality ofthin linear grooves extending in the direction Z. The breakage traceformed surface 132 is connected to the linear trace formed surface 131.The breakage trace formed surface 132 is formed with a breakage trace.The breakage trace is an irregular trace formed when a metal is tornoff. As shown in FIG. 6, in this embodiment, the linear trace formedsurface 131 is closer to the reverse surface 12 than the breakage traceformed surface 132 is. When the chip resistor 101 is mounted on a mountboard 801, the linear trace formed surface 131 is covered by the solderlayer 802. According to this arrangement, solder moves along the thingrooves of the linear trace formed surface 131, whereby a relativelylarge area of the side surface 13 is covered by the solder layer 802.Unlike this embodiment, the breakage trace formed surface 132 may becloser to the reverse surface 12 than the linear trace formed surface131 is.

As shown in FIG. 6, similarly to the side surfaces 13, the side surface14 has a linear trace formed surface 141 and a breakage trace formedsurface 142. Since the linear trace formed surface 141 and the breakagetrace formed surface 142 of the side surface 14 are similar to thelinear trace formed surface 131 and the breakage trace formed surface132 of the side surfaces 13, the explanation is omitted.

The structure of the second electrode 2 is similar to that of the firstelectrode 1, which is as follows.

The second electrode 2 is made of an electrically conductive material.Examples of the electrically conductive material include Cu, Ni and Fe.When the chip resistor 101 is mounted on the mount board 801, the secondelectrode 2 is bonded to the solder layer 802. The second electrode 2 iselectrically connected to the pattern electrode (not shown) of the mountboard 801 via the solder layer 802. In this embodiment, the secondelectrode 2 includes a plate-like portion 281 and an inclined portion282.

The plate-like portion 281 extends along the X-Y plane. The plate-likeportion 281 constitutes the most part of the second electrode 2. Theinclined portion 282 is inclined with respect to the X-Y plane.Specifically, the inclined portion 282 is inclined to be deviated towardthe direction Z1 as proceeding further away from the plate-like portion281. The inclined portion 282 is in the form of a strip extending alongthe direction Y. The inclined portion 282 is connected to the plate-likeportion 281.

The second electrode 2 includes a front surface 21, a reverse surface22, two side surfaces 23, a side surface 24 and two curved surfaces 25.

The front surface 21 faces to the direction Z1, whereas the reversesurface 22 faces to the direction Z2. Each of the side surfaces 23, 24and the curved surfaces 25 face to a direction perpendicular to thedirection Z. Specifically, the side surfaces 23 face to the direction Yand the side surface 24 faces to the direction X. The curved surfaces 25are connected to the side surfaces 23 and the side surface 24.

As shown in FIG. 6, the side surface 23 includes a linear trace formedsurface 231 and a breakage trace formed surface 232. Since the lineartrace formed surface 231 and the breakage trace formed surface 232 ofthe side surface 23 are similar to the linear trace formed surface 131and the breakage trace formed surface 132 of the side surface 13, theexplanation is omitted.

As shown in FIG. 6, similarly to the side surfaces 23, the side surface24 has a linear trace formed surface 241 and a breakage trace formedsurface 242. Since the linear trace formed surface 241 and the breakagetrace formed surface 242 of the side surface 24 are similar to thelinear trace formed surface 231 and the breakage trace formed surface232 of the side surfaces 23, the explanation is omitted.

The resistor portion 3 is made of a resistive material. Examples of theresistive material include an alloy of Cu and Mn, an alloy of Ni and Cr,an alloy of Ni and Cu, and an alloy of Fe and Cr. An alloy of Cu and Mnis relatively soft, whereas an alloy of Ni and Cr, an alloy of Ni andCu, and an alloy of Fe and Cr are relatively hard. The resistance of theresistive material forming the resistor portion 3 is higher than theresistance of the electrically conductive material forming the firstelectrode 1 or the second electrode 2. The resistor portion 3 isconnected to first electrode 1 and the second electrode 2. In thisembodiment, the resistor portion 3 is sandwiched between the firstelectrode 1 and the second electrode 2.

In this embodiment, the inclined portion 182 is closer to the resistorportion 3 than the plate-like portion 181 is. Similarly, the inclinedportion 282 is closer to the resistor portion 3 than the plate-likeportion 281 is.

The resistor portion 3 includes a resistor portion front surface 31, aresistor portion reverse surface 32 and two resistor portion sidesurfaces 33.

The resistor portion front surface 31 faces to the same direction as thefront surface 11 or the front surface 21 (i.e., the direction Z1). Theresistor portion reverse surface 32 faces to the opposite direction fromthe resistor portion front surface 31. The resistor portion reversesurface 32 faces to the same direction as the reverse surface 12 or thereverse surface 22 (i.e., the direction Z2). At least part of thereverse surface 12 and at least part of the reverse surface 22 aredeviated from the resistor portion reverse surface 32 toward the side towhich the resistor portion reverse surface 32 faces (i.e., the directionZ2).

Each of the resistor portion side surfaces 33, which are shown in e.g.FIGS. 4 and 6, faces to the direction (direction Y) that crosses thedirection in which the first electrode 1 and the second electrode 2 arespaced apart from each other. As shown in FIG. 6, each resistor portionside surface 33 includes a linear trace formed surface 331 and abreakage trace formed surface 332. Since the linear trace formed surface331 and the breakage trace formed surface 332 are similar to the lineartrace formed surface 131 and the breakage trace formed surface 132,respectively, the explanation is omitted.

As shown in FIG. 1, the first intermediate layer 4 is between the firstelectrode 1 and the resistor portion 3. The first intermediate layer 4is connected to the first electrode 1 and the resistor portion 3. Inthis embodiment, the first intermediate layer 4 is formed when a highenergy beam is directed to the first electrode 1 or the resistor portion3 to bond the first electrode 1 and the resistor portion 3. Thus, thefirst intermediate layer 4 is made of a mixture of the material formingthe first electrode 1 and the material forming the resistor portion 3.

The first intermediate layer 4 includes a wide portion 43 and a narrowportion 44. The wide portion 43 is exposed to the direction Z2. Thenarrow portion 44 is on the direction Z1 side of the wide portion 43.The dimension of the narrow portion 44 in the direction X is smallerthan the dimension of the wide portion 43 in the direction X. Forinstance, the dimension of the wide portion 43 in the direction X is1-1.5 mm, whereas the dimension of the narrow portion 44 in thedirection X is 0.5-1 mm. The wide portion 43 may have burr (not shown)on the surface.

Similarly to the first intermediate layer 4, the second intermediatelayer 5 is between the second electrode 2 and the resistor portion 3.The second intermediate layer 5 is connected to the second electrode 2and the resistor portion 3. In this embodiment, the second intermediatelayer 5 is formed when a high energy beam is directed to the secondelectrode 2 or the resistor portion 3 to bond the second electrode 2 andthe resistor portion 3. Thus, the second intermediate layer 5 is made ofa mixture of the material forming the second electrode 2 and thematerial forming the resistor portion 3. Thus, the second intermediatelayer 5 and the first intermediate layer 4 are made of the samematerial.

The second intermediate layer 5 includes a wide portion 53 and a narrowportion 54. The wide portion 53 is exposed to the direction Z2. Thenarrow portion 54 is on the direction Z1 side of the wide portion 53.The dimension of the narrow portion 54 in the direction X is smallerthan the dimension of the wide portion 53 in the direction X. Forinstance, the dimension of the wide portion 53 in the direction X is1-1.5 mm, whereas the dimension of the narrow portion 54 in thedirection X is 0.5-1 mm. The wide portion 53 may have burr (not shown)on the surface.

A method for manufacturing the chip resistor 101 is described below.

First, as shown in FIGS. 8 and 9, an electrically conductive member 701is prepared. The electrically conductive member 701 is a lead frame inthis embodiment and includes at least three conductive elongated boards711. In the illustrated example, the electrically conductive member 701includes six conductive elongated boards 711. The conductive elongatedboards 711 are elongated in one direction. In the electricallyconductive member 701, the conductive elongated boards 711 are spacedapart from each other in the width direction crossing the longitudinaldirection of one of the conductive elongated boards 711. As shown inFIG. 9, each conductive elongated board 711 is in the form of anelongated rectangle in cross section. In this embodiment, at least threeconductive elongated boards 711 spaced apart from each other areprovided by forming the electrically conductive member 701.

Similarly, as shown in FIGS. 10 and 11, a resistive member 702 isprepared. In this embodiment, the resistive member 702 is a resistiveframe and includes a plurality of resistive elongated boards 721. Inthis embodiment, the resistive member 702 includes five resistiveelongated boards 721. The resistive elongated boards 721 are elongatedin one direction. In the resistive member 702, the resistive elongatedboards 721 are spaced apart from each other in the width directioncrossing the longitudinal direction of the resistive elongated boards721. As shown in FIG. 11, each resistive elongated board 721 is in theform of an elongated rectangle in cross section. In FIG. 10, theresistive member 702 is hatched for easier understanding. This holdstrue for the subsequent plan views. Unlike this embodiment, theresistive member 702 may be a single flat plate large enough to covercollectively all the conductive elongated boards 711 as viewed in plan.

Then, as shown in FIGS. 12 and 13, a resistor aggregate 703 is formed.To form a resistor aggregate 703, the resistive member 702 is bonded toat least three conductive elongated boards 711 of the electricallyconductive member 701. In this embodiment, each of the resistiveelongated boards 721 is bonded to adjacent two of at least threeconductive elongated boards 711. In this process, each of the resistiveelongated boards 721 is arranged between adjacent two of at least threeconductive elongated boards 711.

As a technique for bonding the resistive member 702 to the conductiveelongated boards 711, welding may be employed. Preferably, as thewelding technique, high energy beam welding may be employed. Examples ofthe high energy beam welding include electron beam welding and laserbeam welding. In the case where high energy beam welding is employed, asshown in FIG. 13, high energy beam 881 (electron beam or laser beam) isdirected to the conductive elongated boards 711 or the resistiveelongated boards 721 along the direction Z1, for example. By receivingenergy of the high energy beam 881, the conductive elongated boards 711or the resistive elongated boards 721 melt, whereby the conductiveelongated boards 711 and the resistive elongated boards 721 are bondedto each other. Unlike this embodiment, the conductive elongated boards711 and the resistive member 702 may be bonded by brazing or solderingusing solder or silver paste. Alternatively, the conductive elongatedboards 711 and the resistive member 702 may be bonded by ultrasonicjoining.

Then, as shown in FIGS. 14-16, the resistor aggregate 703 iscollectively divided into a plurality of chip resistors 101. In FIG. 14,each of the regions of the resistor aggregate 703 which are to becomechip resistors 101 is indicated by a double-dashed line. For instance,about 40 chip resistors 101 are obtained from a single resistoraggregate 703. To divide the resistor aggregate 703 into a plurality ofchip resistors 101, two punching dies 831, 832 (see FIG. 15) of a sizecorresponding to the plurality of chip resistors as viewed in plan areused. By pressing the resistor aggregate 703 between the punching die831 and the punching die 832, the resistor aggregate 703 is punched. Bypunching the resistor aggregate 703, the curved surfaces 15 of the firstelectrode 1 or the curved surfaces 25 of the second electrode 2 may beformed.

As shown in FIG. 16, at the same time as the step of punching theresistor aggregate 703 is performed, the step of bending the conductiveelongated boards 711 is performed. In this embodiment, each conductiveelongated board 711 is bent so that portions of the first electrode 1and the second electrode 2 which are relatively close to the resistorportion 3 are shifted toward the direction Z1, or the direction in whichthe high energy beam 881 travels, from a portion of the first electrode1 or the second electrode 2 which is relatively far from the resistorportion 3. In this way, a plurality of chip resistors 101 aremanufactured.

The advantages of the above-noted embodiment are described below.

According to the embodiment, the resistor aggregate 703 is formed bybonding the resistive member 702 to at least three conductive elongatedboards 711. With this arrangement, the number of chip resistors 101obtained per unit length in the direction Y shown in FIG. 14 increases.In this embodiment, the resistor aggregate 703 is collectively dividedby punching into a plurality of chip resistor 101. Thus, it is notnecessary to successively cut chip resistors 101. This enhances themanufacturing efficiency of the chip resistors 101. Thus, the methodaccording to this embodiment is suitable for efficiently manufacturingthe chip resistor 101.

Since the chip resistor 101 is manufactured by punching, the dimensionalaccuracy of the chip resistor 101 as viewed in plan is determined by thedimensional accuracy of the punching dies 831, 832. Accordingly, thedimensional accuracy of the resistor portion 3 of the chip resistor 101in the direction Y is also determined by the dimensional accuracy of thepunching dies 831, 832. Thus, according to the method of thisembodiment, by selecting punching dies 831, 832 of a desired dimensionalaccuracy before punching the resistor aggregate 703, the dimensionalerror in the direction Y of the resistor portions is reduced as comparedwith the conventional method of successively cutting the strips. Whenthe dimensional error in the direction Y of the resistor portions 3 isreduced, a larger number of resistor portions 3 having a desiredresistance are obtained, whereby a larger number of chip resistors 101having a desired resistance are obtained. When the chip resistor 101 hasa desired resistance, the trimming process for adjusting the resistanceof the chip resistor 101 does not need to be performed. In this way, thenumber of chip resistors 101 which require trimming process reduces.This leads to enhancement of the manufacturing efficiency of the chipresistor 101.

In this embodiment, a lead frame is used as the electrically conductivemember 701, and a resistive frame is used as the resistive member 702.Thus, it is not necessary to individually hold a plurality of conductiveelongated boards 711 or a plurality of resistive elongated boards 721,which facilitates handling.

Unlike the conventional method for manufacturing a chip resistor, thisembodiment does not use a reel. Thus, the work of winding a strip of aresistive material or electrically conductive material around a reel isnot necessary. Thus, the use of a large apparatus for winding a striparound a reel is also unnecessary. Since pulling the strip out of thereel is not necessary, the use of a large apparatus for pulling thestrip out of the reel is also unnecessary.

When a reel is used to manufacture a chip resistor, the entireproduction line is stopped if a trouble happens at some point of astrip. Since this embodiment does not use a reel, such a problem doesnot occur.

When electron beam is used as high energy beam 881 to bond theconductive elongated boards 711 and the resistive elongated boards 721to each other, the conductive elongated boards 711 and the resistiveelongated boards 721 need to be placed in a vacuum chamber. In thisembodiment, the dimension of each conductive elongated board 711 orresistive elongated board 721 in the direction Y is about 100 mm. Thus,such a work as cutting the conductive elongated boards 711 or resistiveelongated boards 721 for housing in a vacuum chamber is not necessary.Thus, the method of this embodiment is suitable for efficientlymanufacturing the chip resistors 101.

In this embodiment, the high energy beam 881 is directed along thedirection Z1. According to this arrangement, the energy of the highenergy beam is absorbed relatively easily by portions on the directionZ2 side of the conductive elongated board 711 and the resistiveelongated board 721, so that these portions melt relatively easily. As aresult, the wide portion 43 exposed to the direction Z2 is formed in thefirst intermediate layer 4 of the chip resistor 101. Burrs may be formedon the surface of the wide portion 43. In this embodiment, each of theconductive elongated board 711 is bent so that the portion of the firstelectrode 1 or the second electrode 2 which is close to the resistorportion 3 is deviated toward the direction Z1 side from the portion ofthe first electrode 1 or the second electrode 2 which is distant fromthe resistor portion 3. According to this arrangement, even when burrsare formed on the surface of the wide portion 43, the burrs are in therecessed portion of the chip resistor 101 and not on the direction z1side of the chip resistor 101. Thus, when the chip resistor 101 is heldby a holder (not shown) for movement, the holder does not come intocontact with the burrs. This allows the chip resistor 101 to be movedstably.

Unlike this embodiment, the lead frame may not be used. As shown inFIGS. 17 and 18, as the electrically conductive member 701, a pluralityof conductive elongated boards 711 separate from each other may beplaced on a pallet 882. Similarly, as the resistive member 702, theresistive frame may not be used. As shown in FIGS. 17 and 18, resistiveelongated boards 721 may be placed between the conductive elongatedboards 711 on the pallet 882. Then, after the conductive elongatedboards 711 and the resistive elongated boards 721 are placed on thepallet 882, the conductive elongated boards 711 and the resistiveelongated boards 721 are bonded to each other.

Other embodiments of the present invention are described below. In thefigures referred to in these embodiments, the elements that areidentical or similar to those of the foregoing embodiment are designatedby the same reference signs as those used for the foregoing embodiment.

The second embodiment of the present invention is described below.

FIG. 19 is a sectional view of a chip resistor mount structure of thisembodiment. FIG. 20 is a sectional view taken along lines XX-XX in FIG.19. FIG. 21 is a sectional view taken along lines XXI-XXI in FIG. 19.FIG. 22 is a plan view of the chip resistor mount structure shown inFIG. 19. FIG. 23 is a view (partially omitted) along the XXIII-XXIII inFIG. 19.

The chip resistor 102 shown in these figures differs from the chipresistor 101 mainly in that the thicknesses (dimension in the directionZ) of the first electrode 1 and the second electrode 2 are larger thanthe thickness (dimension in the direction Z) of the resistor portion 3.The first electrode 1 and the second electrode 2 of the chip resistor102 are in the form of a plane extending along X-Y plane. Neither thefirst electrode 1 nor the second electrode 2 includes an inclinedportion.

The method for manufacturing the chip resistor 102 is the same as themethod for manufacturing the chip resistor 101 except that the thicknessof the conductive elongated boards 711 (see FIG. 9) of the electricallyconductive member 701 is larger than the thickness of the resistiveelongated boards 721 (see FIG. 11) of the resistive member 702. Thus,the explanation is omitted. In the method for manufacturing the chipresistor 102, the step of bending the conductive elongated boards 711 isnot performed.

For the same reasons as those described in the first embodiment, thechip resistor 102 of this embodiment is also suitable for enhancing themanufacturing efficiency.

In manufacturing the chip resistor 102 of this embodiment, a lead frameis used as the electrically conductive member 701, and a resistive frameis used as the resistive member 702. Thus, it is not necessary toindividually hold a plurality of conductive elongated boards 711 or aplurality of resistive elongated boards 721, which facilitates handling.

Unlike the conventional method for manufacturing a chip resistor, thisembodiment does not use a reel. Thus, the work of winding a strip of aresistive material or electrically conductive material around a reel isnot necessary. Thus, the use of a large apparatus for winding a striparound a reel is also unnecessary. Since pulling the strip out of thereel is not necessary, the use of a large apparatus for pulling thestrip out of the reel is also unnecessary.

When a reel is used to manufacture a chip resistor, the entireproduction line is stopped if a trouble happens at some point of astrip. Since this embodiment does not use a reel, such a problem doesnot occur.

In manufacturing the chip resistor 102 of this embodiment, such a workas cutting the conductive elongated boards 711 or resistive elongatedboards 721 for housing in a vacuum chamber is not necessary. Thus, themethod of this embodiment is suitable for efficiently manufacturing thechip resistors 102.

The third embodiment of the present invention is described below.

FIG. 24 is a sectional view of a mount structure of the chip resistoraccording to this embodiment. FIG. 25 is a plan view of the chipresistor mount structure shown in FIG. 24. FIG. 26 is a view (partiallyomitted) along lines XXVI-XXVI in FIG. 24.

The chip resistor 103 shown in these figures differs from the chipresistor 102 of the second embodiment in that the first electrode 1 andthe second electrode 2 are on the same side of the resistor portion 3.Since other structures are the same, the description is omitted.

A method for manufacturing the chip resistor 103 is described below.

First, an electrically conductive member 701 and a resistive member 702are prepared, in the same manner as that described with reference toFIGS. 8-11.

Then, as shown in FIGS. 27 and 28, a resistor aggregate 703 is formed.To form a resistor aggregate 703, the resistive member 702 is bonded toat least three conductive elongated boards 711 of the electricallyconductive member 701. In this embodiment, each of a plurality ofresistive elongated boards 721 is bonded to adjacent two of at leastthree conductive elongated boards 711. In this process, each of theresistive elongated boards 721 is arranged to overlap both of theadjacent two of the at least three conductive elongated boards 711 asviewed in the direction Z.

After the resistor aggregate 703 is formed, the above-described step ofpunching the resistor aggregate 703 is performed, whereby the chipresistor 103 is obtained. In the method for manufacturing the chipresistor 103 as well, the step of bending the conductive elongatedboards 711 is not performed.

For the same reasons as those described in the first embodiment, thechip resistor 102 of this embodiment is also suitable for enhancing themanufacturing efficiency.

In manufacturing the chip resistor 103 of this embodiment, a lead frameis used as the electrically conductive member 701, and a resistive frameis used as the resistive member 702. Thus, it is not necessary toindividually hold a plurality of conductive elongated boards 711 or aplurality of resistive elongated boards 721, which facilitates handling.

Unlike the conventional method for manufacturing a chip resistor, thisembodiment does not use a reel. Thus, the work of winding a strip of aresistive material or electrically conductive material around a reel isnot necessary. Thus, the use of a large apparatus for winding a striparound a reel is also unnecessary. Since pulling the strip out of thereel is not necessary, the use of a large apparatus for pulling thestrip out of the reel is also unnecessary.

When a reel is used to manufacture a chip resistor, the entireproduction line is stopped if a trouble happens at some point of astrip. Since this embodiment does not use a reel, such a problem doesnot occur.

In manufacturing the chip resistor 103 of this embodiment, such a workas cutting the conductive elongated boards 711 or resistive elongatedboards 721 for housing in a vacuum chamber is not necessary. Thus, themethod of this embodiment is suitable for efficiently manufacturing thechip resistors 103.

When current flows through the chip resistor 103, the portion of theresistor portion 3 which overlaps the gap between the first electrode 1and the second electrode 2 as viewed in plan (viewed in the direction Z)functions as a resistor. Thus, the resistance of the chip resistor 103is determined by the distance between the first electrode 1 and thesecond electrode 2. Thus, by adjusting the distance between the firstelectrode 1 and the second electrode 2 in the state of the resistoraggregate 703, the resistance of the chip resistor 103 is finelyadjusted to a desired value. Fine adjustment of the resistance of thechip resistor 103 leads to reduction of the number of chip resistors 101that require the trimming process. This is suitable for enhancing themanufacturing efficiency of the chip resistor 103.

A fourth embodiment of the present invention is described below.

FIG. 29 is a sectional view of a mount structure of the chip resistoraccording to the fourth embodiment of the present invention. FIG. 30 isa sectional view taken along lines XXX-XXX in FIG. 29. FIG. 31 is asectional view taken along lines XXXI-XXXI in FIG. 29. FIG. 32 is a planview of the chip resistor mount structure shown in FIG. 29. FIG. 33 is aview (partially omitted) along lines XXXIII-XXXIII in FIG. 29.

The chip resistor mount structure 805 shown in these figures includes achip resistor 201, a mount board 801 and a solder layer 802.

For instance, the mount board 801 is a printed circuit board. Forinstance, the mount board 801 includes an insulating substrate and apattern electrode (not shown) formed on the insulating substrate. Thechip resistor 301 is mounted on the mount board 801. The solder layer802 is between the chip resistor 201 and the mount board 801. The solderlayer 802 bonds the chip resistor 201 and the mount board 801 to eachother.

The chip resistor 201 includes a first electrode 1, a second electrode2, a resistor portion 3, a first intermediate layer 4 and a secondintermediate layer 5.

As shown in FIGS. 32 and 33, the first electrode 1 includes a frontsurface 11, a reverse surface 12, a side surface 13 a (first electrodeside surface), a side surface 13 b (second electrode side surface) and aside surfaces 14.

The front surface 11 and the reverse surface 12 face away from eachother. Specifically, the front surface 11 faces to the direction Z1,whereas the reverse surface 12 faces to the direction Z2. The sidesurface 13 a faces to one side in the direction Y, whereas the sidesurface 13 b faces to the other side in the direction Y. The sidesurface 14 faces to the direction X. Unlike the chip resistor 101, thefirst electrode 1 of this embodiment does not have a curved surface 15.Thus, the side surface 14 is directly connected to the side surface 13 aand the side surface 13 b.

FIG. 34 is a front view of the chip resistor shown in FIG. 29. FIG. 35is a rear view of the chip resistor shown in FIG. 29.

As shown in FIG. 34, the side surface 13 a includes a linear traceformed surface 131 a (first electrode linear trace formed surface) and abreakage trace formed surface 132 a (first electrode breakage traceformed surface). The breakage trace formed surface 132 a is connected tothe linear trace formed surface 131 a. Since the shapes of the lineartrace formed surface 131 a and the breakage trace formed surface 132 aare the same as those of the linear trace formed surface 131 and thebreakage trace formed surface 132 of the chip resistor 101, thedescription of these is omitted.

In this embodiment, the linear trace formed surface 131 a is closer tothe front surface 11 than the breakage trace formed surface 132 a is. Inthis embodiment, the width (dimension in the direction Z) of the lineartrace formed surface 131 a increases as proceeding further away from theresistor portion 3. The linear trace formed surface 131 a is connectedto the front surface 11. The breakage trace formed surface 132 a isconnected to the reverse surface 12.

As shown in FIG. 35, the side surface 13 b includes a linear traceformed surface 131 b (second electrode linear trace formed surface) anda breakage trace formed surface 132 b (second electrode breakage traceformed surface). The breakage trace formed surface 132 b is connected tothe linear trace formed surface 131 b. Since the shapes of the lineartrace formed surface 131 b and the breakage trace formed surface 132 bare the same as those of the linear trace formed surface 131 and thebreakage trace formed surface 132 of the chip resistor 101, descriptionof these is omitted.

In this embodiment, the linear trace formed surface 131 b is closer tothe reverse surface 12 than the breakage trace formed surface 132 b is.That is, the vertical positional relationship between the breakage traceformed surface and the linear trace formed surface in the side surface13 a is opposite from that in the side surface 13 b. The linear traceformed surface 131 b is connected to the reverse surface 12. Thebreakage trace formed surface 132 b is connected to the front surface11. In this embodiment, the width (dimension in the direction Z) of thelinear trace formed surface 131 b increases as proceeding further awayfrom the resistor portion 3.

The side surface 14 may include the linear trace formed surface 141 andthe breakage trace formed surface 142 similarly to the chip resistor 101or may be a flat surface. The shape or structure of the side surface 14is determined by how the conductive elongated boards 711, which isdescribed later, are made.

Except the points described above, the first electrode 1 has the samestructure as that of the first electrode 1 of the chip resistor 101.Description of the same points is omitted.

As shown in FIGS. 32 and 33, the second electrode 2 includes a frontsurface 21, a reverse surface 22 and side surfaces 23 a, 23 b, 24 b.

The front surface 21 and the reverse surface 22 face away from eachother. Specifically, the front surface 21 faces to the direction Z1,whereas the reverse surface 22 faces to the direction Z2. The sidesurface 23 a faces to one side in the direction Y, whereas the sidesurface 23 b faces to the other side in the direction Y. The sidesurface 24 faces to the direction X. Unlike the chip resistor 101, thesecond electrode 2 of this embodiment does not have a curved surface 25.Thus, the side surface 24 is directly connected to the side surface 23 aand the side surface 23 b.

As shown in FIG. 34, the side surface 23 a includes a linear traceformed surface 231 a and a breakage trace formed surface 232 a. Thebreakage trace formed surface 232 a is connected to the linear traceformed surface 231 a. Since the shapes of the linear trace formedsurface 231 a and the breakage trace formed surface 232 a are the sameas those of the linear trace formed surface 131 and the breakage traceformed surface 132 of the chip resistor 101, description of these isomitted.

In this embodiment, the linear trace formed surface 231 a is closer tothe front surface 21 than the breakage trace formed surface 232 a is. Inthis embodiment, the width (dimension in the direction Z) of the lineartrace formed surface 231 a increases as proceeding further away from theresistor portion 3. The linear trace formed surface 231 a is connectedto the front surface 21. The breakage trace formed surface 232 a isconnected to the reverse surface 22.

As shown in FIG. 35, the side surface 23 b includes a linear traceformed surface 231 b and a breakage trace formed surface 232 b. Thebreakage trace formed surface 232 b is connected to the linear traceformed surface 231 b. Since the shapes of the linear trace formedsurface 231 b and the breakage trace formed surface 232 b are the sameas those of the linear trace formed surface 131 and the breakage traceformed surface 132 of the chip resistor 101, description of these isomitted.

In this embodiment, the linear trace formed surface 231 b is closer tothe reverse surface 22 than the breakage trace formed surface 232 b is.That is, the vertical positional relationship between the breakage traceformed surface and the linear trace formed surface in the side surface23 a is opposite from that in the side surface 23 b. The linear traceformed surface 231 b is connected to the reverse surface 22. Thebreakage trace formed surface 232 b is connected to the front surface21. In this embodiment, the width (dimension in the direction Z) of thelinear trace formed surface 231 b increases as proceeding further awayfrom the resistor portion 3.

The side surface 24 may include the linear trace formed surface 241 andthe breakage trace formed surface 242 similarly to the chip resistor 101or may be a flat surface. The shape or structure of the side surface 24is determined by how the conductive elongated boards 711 are made.

Except the points described above, the second electrode 2 has the samestructure as that of the second electrode 2 of the chip resistor 101.Description of the same points is omitted.

As shown in FIGS. 32 and 33, the resistor portion 3 includes a resistorportion front surface 31, a resistor portion reverse surface 32, aresistor portion side surface 33 a (first resistor portion side surface)and a resistor portion side surface 33 b (second resistor portion sidesurface).

The resistor portion front surface 31 faces to the same direction as thefront surface 11 or the front surface 21 (i.e., the direction Z1). Theresistor portion reverse surface 32 faces to the opposite direction fromthe resistor portion front surface 31. The resistor portion reversesurface 32 faces to the same direction as the reverse surface 12 or thereverse surface 22 (i.e., the direction Z2). At least part of thereverse surface 12 and at least part of the reverse surface 22 aredeviated from the resistor portion reverse surface 32 toward the side towhich the resistor portion reverse surface 32 faces (i.e., the directionZ2).

The resistor portion side surface 33 a shown in e.g. FIG. 32 faces to afirst side in the direction Y. As shown in FIG. 34, the resistor portionside surface 33 a includes a linear trace formed surface 331 a (firstresistor portion linear trace formed surface) and a breakage traceformed surface 332 a (first resistor portion breakage trace formedsurface). The breakage trace formed surface 332 a is connected to thelinear trace formed surface 331 a. Since the shapes of the linear traceformed surface 331 a and the breakage trace formed surface 332 a are thesame as those of the linear trace formed surface 131 and the breakagetrace formed surface 132 of the chip resistor 101, description of theseis omitted.

As shown in FIG. 34, in this embodiment again, the linear trace formedsurface 331 a is closer to the resistor portion front surface 31 thanthe breakage trace formed surface 332 a is. The linear trace formedsurface 331 a is connected to the resistor portion front surface 31. Thebreakage trace formed surface 332 a is connected to the resistor portionreverse surface 32. When the material forming the first electrode 1 orthe second electrode 2 is harder than the material forming the resistorportion 3, the width of the breakage trace formed surface 332 a maybecome larger than the width of the breakage trace formed surface 132 aand the width of the breakage trace formed surface 232 a, as shown inFIG. 34.

The resistor portion side surface 33 b shown in e.g. FIG. 32 faces to asecond side in the direction Y. The resistor portion side surface 33 bis connected to the side surface 13 b of the first electrode 1 and theside surface 23 b of the second electrode 2. As shown in FIG. 35, theresistor portion side surface 33 b includes a linear trace formedsurface 331 b (second resistor portion linear trace formed surface) anda breakage trace formed surface 332 b (second resistor portion breakagetrace formed surface). The breakage trace formed surface 332 b isconnected to the linear trace formed surface 331 b. Since the shapes ofthe linear trace formed surface 331 b and the breakage trace formedsurface 332 b are the same as those of the linear trace formed surface131 and the breakage trace formed surface 132 of the chip resistor 101,description of these is omitted.

In this embodiment, the linear trace formed surface 331 b is closer tothe resistor portion reverse surface 32 than the breakage trace formedsurface 332 b is. That is, the vertical positional relationship of thebreakage trace formed surface and the linear trace formed surface in theresistor portion side surface 33 a is opposite from that in the resistorportion side surface 33 b. The linear trace formed surface 331 b isconnected to the resistor portion reverse surface 32. The breakage traceformed surface 332 b is connected to the resistor portion front surface31.

Except the points described above, the resistor portion 3 has the samestructure as that of the resistor portion 3 of the chip resistor 101.Description of the same points is omitted.

A method for manufacturing the chip resistor 201 is described below.

First, as shown in FIGS. 36 and 38, two conductive elongated boards 711and a resistive elongated board 721 are prepared. The conductiveelongated boards 711 are made of an electrically conductive material.The resistive elongated board 721 is made of a resistive material. Inthis embodiment, the two conductive elongated boards 711 have the samewidth (dimension in the width direction).

Then, the resistive elongated board 721 is to be placed between the twoconductive elongated boards 711. In this embodiment, the resistiveelongated board 721 is arranged between the two conductive elongatedboards 711 as these boards are placed on a base 870 (see FIG. 38).

Then, the two conductive elongated boards 711 are fixed to the resistiveelongated board 721. In this embodiment, a first clamping tool 871 and asecond clamping tool 872 are used to fix the two conductive elongatedboards 711 to the resistive elongated board 721. Specifically, the twoconductive elongated boards 711 and the resistive elongated board 721are sandwiched by the first clamping tool 871 and the second clampingtool 872. One of the two conductive elongated boards 711 is pressedagainst the resistive elongated board 721 by the first clamping tool871, and the other one of the two conductive elongated boards 711 ispressed against the resistive elongated board 721 by the second clampingtool 872.

As shown in FIGS. 39-41, in this embodiment, the two conductiveelongated boards 711 and the resistive elongated board 721 placed on thebase 870 are pressed against the base 870 by a pressing tool 875. Thisprevents the two conductive elongated boards 711 and the resistiveelongated board 721 from rising from the base 870. In FIG. 40, thepressing tool 875 is hatched for easier understanding. The pressing tool875 has two elongated holes 875 a and 875 b. Each of the elongated holes875 a and 875 b is elongated in one direction. In this embodiment, theelongated holes 875 a and 875 b are rectangular as viewed in plan. Asshown in FIG. 40, in pressing the two conductive elongated boards 711and the resistive elongated board 721 against the base 870 by thepressing tool 875, the elongated hole 875 a is arranged to overlap theportion 891 where one of the two conductive elongated boards 711 and theresistive elongated board 721 are in contact with each other. Similarly,in pressing the two conductive elongated boards 711 and the resistiveelongated board 721 against the base 870 by the pressing tool 875, theelongated hole 875 b is arranged to overlap the portion 892 where theother one of the two conductive elongated boards 711 and the resistiveelongated board 721 are in contact with each other.

Then, as shown in FIGS. 40 and 41, a resistor aggregate 703 is formed.To form the resistor aggregate 703, the two conductive elongated boards711 are bonded to the resistive elongated board 721. As a technique forbonding the conductive elongated boards 711 to the resistive member 721,welding may be employed. Preferably, as the welding technique, highenergy beam welding may be employed. Examples of the high energy beamwelding include electron beam welding and laser beam welding. In thecase where high energy beam welding is employed, as shown in FIG. 41,high energy beam 881 (electron beam or laser beam) is directed to theconductive elongated boards 711 or the resistive elongated boards 721along the direction Z1, for example. In this embodiment, the high energybeam 881 is directed in such a manner as to pass through the elongatedholes 875 a, 875 b. By receiving energy of the high energy beam 881, theconductive elongated boards 711 or the resistive elongated board 721melt, whereby the conductive elongated boards 711 and the resistiveelongated boards 721 are bonded together.

Unlike this embodiment, the conductive elongated boards 711 and theresistive members 721 may be bonded together by brazing or solderingusing solder or silver paste. Alternatively, the conductive elongatedboards 711 and the resistive member 721 may be bonded together byultrasonic joining.

Then, as shown in FIGS. 42 and 43, the resistor aggregate 703 is cut byshearing. The resistor aggregate 703 is cut along the double-dashedlines shown in FIG. 40. That is, the two conductive elongated boards 711and the resistive elongated board 721 are cut by shearing along thewidth direction crossing the longitudinal direction of one of the twoconductive elongated boards 711. In this embodiment, the resistoraggregate 703 is successively cut from an end.

To cut the resistor aggregate 703, a die member 841 and a die member 843are used. As shown in FIG. 42, when the die member 841 is moved down,the die member 841 and the die member 843 cut into the conductiveelongated boards 711 and the resistive elongated board 721. (Althoughonly the resistive elongated board 721 is shown in FIG. 42, the samehappens to the conductive elongated board 711 as well). In this process,the die member 841 and the die member 843 form linear traces in theconductive elongated boards 711 and the resistive elongated board 721.The formation of linear traces in the conductive elongated board 711 bythe die member 843 provides the above-described linear trace formedsurfaces 131 a, 231 a. The formation of linear traces in the resistiveelongated board 721 by the die member 843 provides the above-describedlinear trace formed surface 331 a. The formation of linear traces in theconductive elongated board 711 by the die member 841 provides theabove-described linear trace formed surfaces 131 b, 231 b. The formationof linear traces in the resistive elongated board 721 by the die member841 provides the above-described linear trace formed surface 331 b.

When the die member 841 is further moved down as shown in FIG. 43, theshear load exerted on the conductive elongated board 711 and theresistive elongated board 721 increases. Thus, breakage occurs in theconductive elongated board 711 and the resistive elongated board 721,whereby the conductive elongated board 711 and the resistive elongatedboard 721 are cut off. In this process, breakage traces are formed inthe conductive elongated board 711 and the resistive elongated board721. The formation of breakage traces in the conductive elongated board711 or the resistive elongated board 721 provides the above-describedbreakage trace formed surfaces.

In this embodiment, at the same time as the step of cutting the resistoraggregate 703 (the step of cutting the conductive elongated board 711and the resistive elongated board 721 by shearing), the step of bendingeach conductive elongated board 711 is performed. That is, as shown inFIGS. 42-45, in performing shearing by the die member 841 and the diemember 843, the conductive elongated board 711 and the resistiveelongated board 721 are sandwiched by the die member 841 and the diemember 842. As shown in FIG. 44, the die member 841 is formed with aprojection 841 a, whereas the die member 842 is formed with a recess 842a. Thus, when the conductive elongated boards 711 and the resistiveelongated board 721 are sandwiched by the die member 841 and the diemember 842, the conductive elongated boards 711 are bent so that a partof the chip resistor 201 projects downward in FIG. 44. Since theprojection 841 a is pressed against the resistive elongated board 721,the resistive elongated board 721 may be sheared prior to the conductiveelongated boards 711. In this way, a single chip resistor 201 shown inFIG. 29 is obtained.

By repeating the process steps similar to those described with referenceto FIGS. 42-45, a plurality of chip resistors 201 are obtained from theresistor aggregate 703.

Unlike this embodiment, the step of cutting the resistor aggregate 703(the step of cutting the conductive elongated boards 711 and theresistive elongated board 721 by shearing) and the step of bending theconductive elongated boards 711 may not be performed at the same time.For instance, the conductive elongated boards 711 may be bent before thestep of cutting the resistor aggregate 703 (the step of cutting theconductive elongated boards 711 and the resistive elongated board 721 byshearing).

The advantages of this embodiment are described below.

In this embodiment, two conductive elongated boards 711 and theresistive elongated board 721 are cut by shearing. Unlike the case wherethe conductive elongated board 711 and the resistive elongated board 721are cut by dicing, the method of this embodiment does not leaveshavings. Thus, relatively large portions of the conductive elongatedboard 711 and resistive elongated board 721 are used for the chipresistor 201. In other words, the portions of the conductive elongatedboard 711 and resistive elongated board 721 which are wasted, i.e., notused for the chip resistor 201, are reduced. The conductive elongatedboard 711 and the resistive elongated board 721 are efficiently used formaking chip resistors 201.

In this embodiment, the step of bending the conductive elongated boards711 is performed at the same time as the step of cutting the conductiveelongated boards 711 and the resistive elongated board 721. Thisshortens the time required for manufacturing the chip resistor 201.

In this embodiment, the two conductive elongated boards 711 are fixed tothe resistive elongated board 721 before the two conductive elongatedboards 711 and the resistive elongated board 721 are bonded to eachother. In the step of bonding the two conductive elongated boards 711and the resistive elongated board 721, welding is performed, with theconductive elongated boards 711 fixed to the resistive elongated board721. With this arrangement, in bonding the conductive elongated boards711 and the resistive elongated board 721, the conductive elongatedboards 711 and the resistive elongated board 721 are prevented frommoving. Thus, the conductive elongated boards 711 and the resistiveelongated board 721 are reliably bonded to each other.

According to this embodiment, the elongated hole 875 a is arranged tooverlap the portion 891 where one of the two conductive elongated boards711 and the resistive elongated board 721 are in contact with eachother, and the elongated hole 875 b is arranged to overlap the portion892 where the other one of the two conductive elongated boards 711 andthe resistive elongated board 721 are in contact with each other. Thehigh energy beam 881 is directed so as to pass through the elongatedholes 875 a and 875 b. With this arrangement, the high energy beam 881is reliably directed to the portion 891 and the portion 892, with theconductive elongated boards 711 and the resistive elongated board 721prevented from rising from the base 870. Thus, the high energy beam 881is reliably directed to desired portions.

A fifth embodiment of the present invention is described below.

FIG. 46 a sectional view of a mount structure of a chip resistoraccording to the fifth embodiment of the present invention.

The chip resistor 202 shown in this figure differs from the chipresistor 201 in that the thickness of the resistor portion 3 isdifferent from the thickness of the first electrode 1 or the secondelectrode 2. In this embodiment, the thickness of the resistor portion 3is larger than that of the first electrode 1 or the second electrode 2.The thickness of the resistor portion 3 may be smaller than that of thefirst electrode 1 or the second electrode 2.

To manufacture the chip resistor 202, a pressing tool having a structuredifferent from that of the pressing tool 875 is used to press the twoconductive elongated boards 711 and the resistive elongated board 721against the base 870. Except this point, the chip resistor 202 ismanufactured in the same way as the chip resistor 201. However, thethickness of the resistive elongated board 721 is larger than that ofthe conductive elongated boards 711.

As shown in FIGS. 47-49, the pressing tool 875 includes a resistorpressing member 876 and conductor pressing members 877 and 878. In FIG.48, the pressing tool 875 is hatched for easier understanding. Theresistor pressing member 876 and the conductor pressing members 877 and878 are separately prepared. The resistor pressing member 876 pressesthe resistive elongated board 721 against the base 870. The conductorpressing member 877 presses one of the two conductive elongated boards711 against the base 870. The conductor pressing member 878 presses theother one of the two conductive elongated boards 711 against the base870. In this embodiment, an elongated hole 875 a is defined between theconductor pressing member 877 and the resistor pressing member 876, andan elongated hole 875 b is defined between the conductor pressing member878 and the resistor pressing member 876. In this embodiment again, highenergy beam 881 is directed to pass through the elongated holes 875 aand 875 b.

By using the resistor pressing member 876 and the conductor pressingmembers 877, 878 which are separately prepared, both of the resistiveelongated board 721 and the two conductive elongated boards 711 arereliably pressed against the base 870 by the resistor pressing member876 and the conductor pressing members 877, 878 even when the resistiveelongated board 721 and the conductive elongated boards 711 havedifferent thicknesses. Thus, high energy beam 881 is directed to theportion 891 and the portion 892, with the conductive elongated boards711 and the resistive elongated board 721 prevented from rising from thebase 870. This assures that high energy beam 881 is directed to desiredportions.

According to this embodiment, the same advantages as those of the fourthembodiment are obtained.

The present invention is not limited to the foregoing embodiments. Thespecific structure of each part of the present invention may be variedin design in many ways.

The invention claimed is:
 1. A chip resistor comprising: a firstelectrode; a second electrode spaced apart from the first electrode in afirst direction; and a resistor portion bonded to the first electrodeand the second electrode, wherein the resistor portion extends along aplane spreading in the first direction and a second direction crossingthe first direction, and wherein the first electrode includes: an innerside surface adjacent to the resistor portion; a first side surfacespaced apart from the inner side surface in the first direction, thefirst side surface and the inner side surface being located on oppositesides of the first electrode in the first direction; a second sidesurface facing in the second direction; and a curved surface directlyconnected to both the first side surface and the second side surface. 2.The chip resistor according to claim 1, further comprising a firstintermediate layer and a second intermediate layer, the firstintermediate layer connected to the first electrode and the resistorportion, the second intermediate layer connected to the second electrodeand the resistor portion, wherein the first intermediate layer and thesecond intermediate layer are made of a same material.
 3. The chipresistor according to claim 2, wherein the resistor portion issandwiched between the first electrode and the second electrode.
 4. Thechip resistor according to claim 2, wherein the first intermediate layerincludes a wide portion and a narrow portion, and the wide portion isexposed to a third direction crossing both of the first direction andthe second direction, and a dimension of the narrow portion in the firstdirection is smaller than a dimension of the wide portion in the firstdirection.
 5. The chip resistor according to claim 1, wherein the firstelectrode and the second electrode are on a same side of the resistorportion.
 6. The chip resistor according to claim 1, wherein the firstside surface includes a linear trace formed surface formed with a lineartrace, and a breakage trace formed surface connected to the linear traceformed surface and formed with a breakage trace.
 7. The chip resistoraccording to claim 1, wherein the first electrode includes a plate-likeportion extending along the first direction and the second direction andan inclined portion inclined with respect to the plate-like portion andcloser to the resistor portion than the plate-like portion is.
 8. Thechip resistor according to claim 1, wherein the resistor portion has athickness smaller than a thickness of the first electrode.